1. Field of the Invention
The present invention relates generally to motor fuel containing certain hydrazine derivatives which improve the performance characteristics of the fuel. More specifically, the invention is directed to improved gasoline and gasoline-alcohol (gasohol) blends which contain an aromatic hydrazine additive, and exhibit increased octane number, enhanced misibility, low temperature stability, and reduced corrosiveness toward engine parts, as compared to the same fuel blend without such additive. This invention also pertains to methods for imparting such desirable performance characteristics to motor fuels.
2. Description of the Prior Art
The term "gasohol" is generally applied to a motor fuel comprising a blend of gasoline or other liquid hydrocarbons with various lower alcohols, particularly methanol or ethanol. Typically, such fuel mixtures contain, by volume, approximately 90 to 95% gasoline and 5 to 10% alcohol.
One of the notable advantages of blending gasoline with a lower alcohol is an increase in octane number, permitting less costly petroleum stocks to be used for making gasohol. Octane number is a measure of the degree of knocking of a fuel mixture under standard test conditions. Octane numbers may be reported as motor octane numbers, which are determined under actual road operating conditions or as research octane numbers, which are obtained under test or laboratory conditions. Research octane numbers generally run about 10 points higher than motor octane numbers. A high octane number is one of the essential requirements of a good motor fuel. A fuel blend comprising, by volume, 90% unleaded gasoline and 10% ethanol, for example, has a motor octane number of about 92, whereas unleaded gasoline alone has a motor octane number of about 89.
The increased octane number obtained by blending gasoline with a lower alcohol is offset by several serious drawbacks. First, the addition of a lower alcohol to gasoline generally increases its vapor pressure and adversely affects its distillation characteristics, which may result in hard starting and vapor lock in hot weather, as well as making engine warm-up difficult in cold weather. Second, in comparision to gasoline, the lower alcohols, as a group, have a relatively low heat content or energy value, so that mixing alcohol with gasoline may reduce fuel economy, i.e. lower mileage per gallon. Third, the stability of gasoline-alcohol blends is significantly influenced by variations in composition and temperature. For example, blends having a methanol content of about 10 volume percent or more are susceptible to phase separation, particularly at temperatures below 0.degree. C. The stability problem is exacerbated by the presence of water in the blend. Even as little as a fraction of one-percent of water in certain gasoline-alcohol blends may cause "splitting" of the blend, i.e. separation into an aqueous alcohol phase and a gasoline-hydrocarbon phase. Such separation may cause starting problems, rough engine operation, and fuel-line plugging. Accordingly, anhydrous alcohol must be used for blending with gasoline and extreme care must be exercised so that that the alcohol remains substantially anhydrous during transporation and storage. Fourth, the lower alcohols readily pick up water, and become oxidized in the presence of water, forming aldehydes and acids which tend to corrode metals and cause degradation of plastics, and thus may severly damage engine parts, fuel tanks and fittings, particularly those made of aluminum.
Among the gasoline-alcohol blends that have been tried as motor fuels, the foregoing problems have been most evident with gasoline-methanol blends. Ethanol, although a more desirable fuel component than methanol from a performance standpoint, costs considerably more to produce. Indeed, most previous attempts at large scale marketing of gasoline-ethanol blends have required some sort of tax incentive or subsidy.
If crude oil prices continue to increase and more efficient processes for the manufacture of ethanol become available, gasohol will undoubtedly become price competitive with gasoline. However, even at a competitive price, it is unlikely that gasohol will account for a significant proportion of motor fuel consumption, unless the aforementioned performance problems can be overcome, and the miscibility of alcohol in gasoline can be increased.
In my U.S. Pat. No. 4,081,252, there is described a method for improving the combustion of various fuels, such as ammonia, petroleum distillates, alcohols, amines, or mixtures of such fuels, by adding to the fuel any of a number of hydrogen-carrier compounds for releasing energy and hydrogen at the time of ignition. Among the hydrogen-carrier compounds disclosed as being preferred for admixing with petroleum distillates, e.g. gasoline, are hydrazines, especially alkly hydrazines, such as unsymmetrical dimethyl hydrazine (UDMH). The preference for hydrazines, it is disclosed, is due to the siginficant reduction of undesirable emissions and increased efficiency upon combustion of the resultant fuel mixture. Among the hydrazine additive-containing fuel compositions disclosed in my aforesaid patent, are compositions in which the base fuel is a petroleum distillate or a mixture of gasoline, 20% methanol and 0.5% water. Upon further evaluation of such fuel compositions, however, it has now been discovered that the motor octane number is reduced to an unacceptably low level. These fuel compositions have been determined to have motor octane numbers in the range of about 50 to about 60, which is too low for use as motor fuels.